This proposal requests support for a Symposium on recent developments in Photodynamic Therapy, to be held in conjunction with the 2002 meeting of the American Society for Photobiology in Quebec City, Canada. An organizing committee has been identified, and the meeting will be able to take advantage of the ASP facilities with regard to hotel selection, announcements and mechanisms for dealing with proffered papers and poster proposals. Since there is no other major PDT conference in 2002, this will be an opportunity for workers in the field to receive updates on research from major laboratories and exchange additional information. The meeting will concentrate on: mechanisms of cell death, cellular responses to PDT and photosensitized inactivation of molecular targets. This will encompass the three modes of cell death but also include some of the newer work on induction of cytokines and the use of PDT to approach some of the molecular targets (e.g., growth factor receptors and PKC). The typical registration for ASP meetings is 350-400, but the addition of a substantial PDT symposium is expected to attract additional participants. The most recent PDT meeting, sponsored by the International Photodynamic Assn, has more than 600 participants.